This invention relates to automatic liquid level sensors for container filling devices which are used primarily in the beverage bottling industry for filling containers having a neck diameter only a little smaller in diameter than the container proper, such as jars. In contrast to the case of filling bottles, in which the liquid is directed along the wall of the bottle from the moment it enters the bottle, it is necessary when filling wide mouthed containers to find another way to guide the liquid from the relatively narrow discharge opening of the filling device to the much larger diameter wall of the container.
With filling devices for jars this is accomplished by producing a freely falling bell-shaped stream, which spreads out parabolically from the discharge opening to the container wall. The outwardly directed radial component of the flow is produced either through rotational momentum induced by a spiral mechanism or by using a centrally positioned, outwardly directed deflector, which may, for example, be located on the return air pipe.
Prior art sensors usually have the form of a float gauge, in which a buoyant ball rises with the level of liquid and is pressed against the lower opening of the return air pipe, sealing it off. This interruption of the return air flow halts the filling process. In consequence, the sensor is always located at the maximum fill level.
This location of the sensor at the maximum fill level is a disadvantage of the usual designs. Since the sensor always lies below the filling device, it necessarily extend past it and is exposed to damage when the containers under the device are moved in and out of position.
In addition, the usual sensor arrangement requires a complicated construction of the filling device. One familiar design provides a lifting mechanism for the container, which lowers the container when it is to be moved aside. Another familiar design has the container move only horizontally, the sealing ring being provided with a lifting mechanism. The sensor must also be raised in this version, usually by means of an arm connecting the sensor to the sealing ring. However, this increases unnecessarily the displacement of the sealing ring. In addition, the arm, which follows an essentially radial path through the bell-shaped stream, disrupts the flow of liquid; this is a disadvantage, especially in the case of carbonated beverages.